/**
 * A child's brief with files its parent already read appended, so the child
 * starts with their current contents instead of spending turns reading them
 * again. Paths resolve against the child's folder. A file that's missing,
 * binary or past the limits is named with the reason, never fatal: the child
 * can still read it itself. Returns the brief unchanged when there are none.
 */
export declare function withContextFiles(task: string, files: readonly string[], cwd: string): Promise<string>;